Unable to sleep at night, Ganta Nakami is cranky in class and unpopular with his classmates. He discovers that the school observatory, once used by the now-defunct astronomy club, may be the perfect place for a nap--but he's not alone. Fellow insomniac Isaki Magari is willing to share the observatory with Nakami, and a friendship between the two begins as they bond over the most unlikely things.
Magari and her friends pass the first winter of high school with cozy sleepovers at Nono's house. As spring arrives, Nakami turns 16, and the couple's second year of high school begins. But with a new grade comes new chaos, and the pair finds their relationship taking steps forward in ways they never expected!